Electric drive axle with lubrication system

ABSTRACT

Methods and systems for an electric drive axle of a vehicle are provided. An electric drive axle system includes, in one example a gear train configured to rotationally attach to an electric motor-generator, the gear train includes an output shaft having a clutch arranged thereon and configured to selectively rotationally couple a gear to the output shaft. The gear train further includes a lubrication channel extending between an output shaft and an axle shaft and including an outlet extending through the output shaft and opening into the clutch.

FIELD

The present disclosure relates to electric drive axles in vehicles, andmore particularly to lubrication systems in the electric drive axles.

BACKGROUND

Electrified axles have been incorporated into electric as well as hybridvehicles to provide or augment vehicle propulsion. The electrified axleshave included gearboxes providing a desired gear reduction between theelectric motor and the drive wheels. Drive axles have also incorporatedlubrication systems routing lubricant to gearings and other componentsto reduce friction in the system. However, drive axle compactness mayaffect the ability of the lubrication system to meet componentlubrication needs. Therefore, axle packaging compactness and componentlubrication needs may be, in certain circumstances, competing designcharacteristics. Lubrication routing issues may be particularlychallenging in drive axles with tightly packaged planetary gear sets.

SUMMARY

To overcome at least some of the aforementioned drawbacks, an electricdrive axle system is provided. In one example, the electric drive axlesystem includes a gear train configured to rotationally attach to anelectric motor-generator. The gear train includes an output shaft havinga clutch arranged thereon and configured to selectively rotationallycouple a gear to the output shaft. The gear train further includes alubrication channel extending between an output shaft and an axle shaftand including an outlet extending through the output shaft and openinginto the clutch. In this way, lubricant is efficiently routed to theclutch in a compact drive axle arrangement.

In another example, the gear may include a tapered inner surfaceconfigured to outflow the lubricant from the clutch. Consequently,lubricant may be radially routed through the clutch and spacedefficiently expelled through a lubrication conduit integrated into asection of the gear.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a vehicle including an electricdrive axle system.

FIG. 2 shows a perspective view of an example of an electric drive axlesystem with a gear train having multiple selectable gear sets.

FIG. 3 shows a top view of the electric drive axle system, depicted inFIG. 2.

FIG. 4 shows a side view of the electric drive axle system, depicted inFIG. 2.

FIG. 5 shows a cross-sectional view of an electric motor-generator andinput shaft in the electric drive axle system, depicted in FIG. 2.

FIG. 6 shows a cross-sectional view of an intermediate shaft in the geartrain of the electric drive axle system, depicted in FIG. 2.

FIG. 7 shows a cross-sectional view of an output shaft, planetary gearassembly, and differential in the gear train of the electric drive axlesystem, depicted in FIG. 2.

FIG. 8 shows a detailed view of the output shaft, planetary gearassembly, and differential in the gear train of the electric drive axlesystem, depicted in FIG. 2.

FIG. 9 shows a detailed view of the clutch assemblies in the gear trainof the electric drive axle system, depicted in FIG. 2.

FIG. 10 shows a detailed view of the second clutch assembly included inthe electric drive axle, depicted in FIG. 9.

FIG. 11 shows a detailed view of a section of the output shaft, shown inFIG. 10.

FIG. 12 shows a detailed view of a friction disk carrier included in thesecond clutch assembly, depicted in FIG. 10.

FIG. 13 shows a detailed illustration of a clutch drum included in thesecond clutch assembly, depicted in FIG. 10.

FIG. 14 shows a detailed view of the first clutch assembly, depicted inFIG. 9.

FIGS. 15-16 show detailed view of the fifth gear and the dog clutchteeth corresponding to the first clutch assembly shown in FIG. 9.

FIG. 17 shows a method for operation of a lubrication system in anelectric drive axle.

FIGS. 18-20 show power paths for different operating modalities of theelectric drive axle system, depicted in FIG. 2.

FIG. 21 shows an example of a one-way clutch.

FIGS. 2-16 and 18-21 are drawn approximately to scale. However, otherrelative dimensions of the components may be used in other embodiments.

DETAILED DESCRIPTION

A lubrication system for a friction clutch in an electric drive axle isdescribed herein. The lubrication system efficiently routes lubricant tothe friction clutch via a lubrication channel in a space between anouter circumference of an axle shaft and an inner circumference of anoutput shaft of a gearbox. In one example, the lubricant may be routedthrough a first outlet of the lubrication channel extending radiallythrough the output shaft and a friction disk carrier to supply frictiondisks in the clutch with a targeted amount of lubricant. In this way,the lubrication needs of the friction clutch may be met in a spaceefficient manner. The lubrication system may further include, in oneexample, a second outlet of the lubrication channel extending throughthe output shaft into a region adjacent to a one-way clutch coupled tothe output shaft. In this way, the lubrication needs of additionalclutches in the electric drive axle may be met, if desired.

FIG. 1 schematically illustrates a vehicle with an electric drive axlesystem designed with multiple gear ratios. FIGS. 2-4 illustratedifferent views of an example of an electric drive axle system. FIG. 5shows a cross-sectional view of an electric motor-generator included inthe electric drive axle system, shown in FIG. 4. FIG. 6 shows across-sectional view of an input shaft and intermediate shaft includedin a gear train in the electric drive axle system, shown in FIG. 4. FIG.7 shows a cross-sectional view of an intermediate shaft and an outputshaft in the gear train in the electric drive axle system, shown in FIG.4. FIG. 8 shows a cross-sectional view of the output shaft included inthe gear train in the electric drive axle system, shown in FIG. 4. FIG.9 shows a detailed view of clutch assemblies in the electric drive axlesystem, shown in FIG. 4. FIG. 10 shows a detailed view of the secondclutch assembly included in the electric drive axle, shown in FIG. 9.FIG. 11 shows a detailed view of a section of the output shaft, shown inFIG. 10. FIG. 12 shows a detailed view of a friction disk carrierincluded in the second clutch assembly, shown in FIG. 10. FIG. 13 showsa detailed illustration of a clutch drum included in the second clutchassembly, shown in FIG. 10. FIG. 14 shows a detailed view of the firstclutch assembly, shown in FIG. 9. FIGS. 15-16 show detailed view of thefifth gear and the dog clutch teeth corresponding to the first clutchassembly shown in FIG. 9. FIG. 17 shows a method for operation of alubrication system in an electric drive axle. FIGS. 18-20 show exemplarygear train power paths occurring during different modes of systemoperation. FIG. 21 shows an exemplary embodiment of a one-way clutch.Exemplary as expressed herein does not give any sort of preferentialindication but rather denotes potential aspects of the system.

FIG. 1 shows a schematic depiction of a vehicle 100 having an electricdrive axle system 102 with a gear train 104 and an electricmotor-generator 106. The stick diagram of FIG. 1 provides a high-leveltopology of the vehicle, gear train, and corresponding components.However, it will be understood that the vehicle, gear train, andcorresponding components have greater structural complexity than iscaptured in FIG. 1. The structural details of various facets of the geartrain 104 are illustrated, by way of example, in greater detail hereinwith regard to FIGS. 2-21.

The electric motor-generator 106 is electrically coupled to an energystorage device 108 (e.g., battery, capacitor, and the like). Arrows 109signify the energy transfer between the electric motor-generator 106 andthe energy storage device 108 that may occur during different modes ofsystem operation. The electric motor-generator 106 may includeconventional components for generating rotational output (e.g., forwardand reverse drive rotational output) and/or electrical energy forrecharging the energy storage device 108 such as a rotorelectromagnetically interacting with a stator, to provide theaforementioned energy transfer functionality. The electricmotor-generator 106 is shown including a rotor shaft 180 with a firstbearing 181 and a second bearing 182 coupled thereto. The first bearing181 may be a fixed bearing and the second bearing 182 may be a floatingbearing. Although the second bearing 182 is shown positioned within themotor-generator, it will be understood that in some embodiments, bearing182 may be coupled to the input shaft to facilitate rotation thereof.Other bearing arrangements with regard to the motor-generator have beencontemplated such as arrangements with alternate quantities and/or typesof bearings.

The vehicle may take a variety of forms in different embodiments. Forexample, the vehicle 100 may be hybrid vehicle where both the electricmotor-generator 106 and an internal combustion engine (not shown) areutilized for motive power generation. For instance, in one use-casehybrid vehicle configuration, the internal combustion engine may assistin recharging the energy storage device 108, during certain conditions.In another use-case hybrid vehicle configuration, the internalcombustion engine may be configured to provide rotational energy to adifferential 110 or other suitable locations in the gear train 104. Inyet another use-case hybrid vehicle configuration, the engine mayprovide rotational input to another drive axle (not shown). Further, inother examples, the vehicle may be a battery electric vehicle (BEV)where the internal combustion engine is omitted.

The rotor shaft 180 of the electric motor-generator 106 is coupled to aninput shaft 112. For instance, the rotor shaft 180 may be transitionfit, slip fit, mechanically attached, in splined engagement,combinations thereof, etc., with an end of the input shaft 112. A firstgear 114 is positioned or formed on the input shaft 112. A bearing 183is shown coupled to the input shaft 112. The bearing 183 may be a fixedbearing, in one example. However, in other examples, the bearing 183 maybe another suitable type of bearing or in some cases may be omitted fromthe system.

A second gear 116 is rotationally coupled to the first gear 114 andresides on an intermediate shaft 118. As described herein, rotationalcoupling between gears or other components may include an interfacebetween the gears where teeth of the gears mesh to facilitate rotationalenergy transfer therebetween. As such, rotational coupling of thecomponents allows rotational energy transfer to be transferred betweenthe corresponding components. Conversely, rotational decoupling mayinclude a state between two components when rotational energy issubstantially inhibited from being transferred between the components.

A third gear 120 and a fourth gear 122 are additionally included on theintermediate shaft 118, although other gearing arrangements have beenenvisioned. Bearings 184 (e.g., tapered roller bearings) are coupled toeither axial end of the intermediate shaft 118 to support the shaft andfacilitate rotation thereof. The tapered roller bearings may decreasethe axle package width when compared to other types of bearing such asball bearings. However, other suitable intermediate shaft bearing typesand/or arrangements have been envisioned. The bearing arrangement on theintermediate shaft as well as the other bearing arrangements describedherein may be selected based on expected shaft loading (e.g., radial andthrust loading), gear size, shaft size, etc.

Continuing with the gear train description, the fourth gear 122 isrotationally coupled to a fifth gear 124 and the third gear 120 isrotationally coupled to a sixth gear 126. The first gear 114, the secondgear 116, the third gear 120, the fourth gear 122, the fifth gear 124,and the sixth gear 126 are included in a gear assembly 130, in theillustrated embodiment. However, the gear assembly may include analternate number of gears and/or have a different layout, in otherembodiments. The number of gears in the assembly and the assembly layoutmay be selected based on end-use design goals related to desired gearrange and packaging, for instance.

The first gear 114, the second gear 116, the fourth gear 122, and thefifth gear 124, may be included in a first gear set 127. Additionally,the first gear 114, the second gear 116, third gear 120, and the sixthgear 126, may be included in a second gear set 129. The first gear set127 may have a higher gear ratio than the second gear set 129, in oneexample. However, other gear arrangements in the different gear sets maybe used, in other examples. Clutch assemblies in the system 102 allowthe first gear set 127 or the second gear set 129 to be placed in anoperational state. To elaborate, the clutch assemblies allow the gearratio delivered to drive wheels 128 on driving surfaces 133, by way ofthe gear assembly 130, a planetary gear assembly 138, and thedifferential 110, to be adjusted. For instance, the clutch assembliesmay be operated to engage the first gear set 127, during certainconditions (e.g., towing, lower speed vehicle operation, etc.), andengage the second gear set 129, during other conditions (e.g., higherspeed vehicle operation). As such, the system may transition between thedifferent gear sets based on vehicle operating conditions, driver input,etc. In this way, the gear train has distinct selectable gear ratios,allowing the gear train to be adapted for different driving conditions,as desired. It will be appreciated that the gear ratio adjustability mayalso be utilized to increase electric motor efficiency, in some cases.

The system 102 may specifically include a first clutch assembly 132 anda second clutch assembly 134. The first clutch assembly 132 isconfigured to rotationally couple and decouple the fifth gear 124 froman output shaft 136. Likewise, the second clutch assembly 134 functionsto rotationally couple and decouple the sixth gear 126 from the outputshaft 136. The first clutch assembly 132 may include a one-way clutch185 (e.g., sprag clutch) and a locking clutch 186 working in conjunctionto accomplish the coupling/decoupling functionality, in a compactarrangement. However, other clutch designs have been contemplated, suchas a friction clutch (e.g., wet friction clutch), a hydraulic clutch, anelectromagnetic clutch, and the like. The structure and function of theone-way and locking clutches are described in greater detail herein. Thesecond clutch assembly 134 may be a wet friction clutch providing smoothengagement/disengagement, in one embodiment. However, in other examples,the second clutch assembly 134 may include additional or alternate typesof suitable clutches (e.g., hydraulic, electromagnetic, etc.).

The output shaft 136 is rotationally coupled to the planetary gearassembly 138, in the illustrated embodiment. The planetary gear assembly138 may include an annulus 187 also referred to as a ring gear, acarrier 188 with planet gears 189 mounted thereon, and a sun gear 190providing a space efficient design capable of providing a relativelyhigh gear ratio in comparison to non-planetary arrangements. In theillustrated embodiment, the sun gear 190 is rotationally coupled to theoutput shaft 136 and the carrier 188 is rotationally coupled to thedifferential 110 (e.g., a differential case). However, in alternateexamples, different gears in the planetary assembly may be rotationallycoupled to the output shaft and the differential. Further, in oneexample, the components of the planetary gear assembly 138 may benon-adjustable with regard to the components that are held stationaryand allowed to rotate. Thus, in one-use case example, the annulus 187may be held substantially stationary and the carrier 188, planet gears189, and the sun gear 190 and the gears stationary/rotational state mayremain unchanged during gear train operation. In the illustratedembodiment, the annulus 187 is fixedly coupled to the motor-generatorhousing, to increase system space efficiency. However, the annulus maybe fixedly coupled to other vehicle structures, in other instances. Byusing a non-adjustable planetary assembly, gear train operation may besimplified when compared to planetary arrangements with gears havingrotational state adjustability. However, adjustable planetaryarrangements may be used in the system, in other embodiments.

Various bearings may be coupled to the output shaft 136 and theplanetary gear assembly 138 to enable rotation of components coupled tothe shaft and assembly and in some cases support the components withregard to radial and/or thrust loads. A bearing 191 (e.g., needle rollerbearing) is shown coupled to the output shaft 136 and the second clutchassembly 134. Additionally, a bearing 192 (e.g., tapered roller bearing)is shown coupled to the second clutch assembly 134. A bearing 193 (e.g.,floating bearing) is also shown coupled to the second clutch assembly134 and the output shaft 136. A bearing 194 (e.g., thrust bearing) mayalso be positioned axially between and coupled to the sixth gear 126 andthe first clutch assembly 132. A bearing 196 (e.g., fixed bearing) mayalso be coupled to the one-way clutch 185. Additionally, a bearing 197(e.g., ball bearing) is shown coupled to the planetary gear assembly 138and a bearing 198 (e.g., ball bearing) is shown coupled to thedifferential case 142. However, other suitable bearing arrangements havebeen contemplated, such as arrangements where the quantity and/orconfigurations of the bearings are varied.

Additionally, FIG. 1 depicts the planetary gear assembly 138 directlyrotationally coupled to the differential 110. Directly coupling theplanetary gear assembly to the differential increases system compactnessand simplifies system architecture. In other examples, however,intermediate gearing may be provided between the planetary gear assemblyand the differential. In turn, the differential 110 is designed torotationally drive an axle 140 coupled to the drive wheels 128. The axle140 is shown including a first shaft section 141 and a second shaftsection 143 coupled to different drive wheels 128. Furthermore, the axle140 is shown arranged within (e.g., co-axial with) the output shaft 136which allows more space efficient design to be achieved. However, offsetaxle-output shaft arrangements may be used, in other examples.

Further in one example, the axle 140 may be a beam axle. A beam axle,also referred to in the art as a solid axle or rigid axle, may be anaxle with mechanical components structurally supporting one another andextending between drive wheels coupled to the axle. Thus, wheels coupledto the axle may move in unison when articulating, during, for example,vehicle travel on uneven road surfaces. For instance, the beam axle maybe a structurally continuous axle spanning the drive wheels on a lateralaxis, in one embodiment. In another embodiment, the beam axle mayinclude co-axial shafts receiving rotational input from different gearsin the differential and structurally supported by the differential.

The differential 110 may include a case 142 housing gearing such aspinion gears, side gears, etc., to achieve the aforementioned energytransfer functionality. To elaborate, the differential 110 may be anelectronic locking differential, in one example. In another example, thedifferential 110 may be an electronic limited slip differential or atorque vectoring dual clutch. In yet other examples, an opendifferential may be used. Referring to the locking differential example,when unlocked, the locking differential may allow the two drive wheelsto spin at different speeds and conversely, when locked, the lockingdifferential may force the drive wheels to rotate at the same speed. Inthis way, the gear train configuration can be adapted to increasetraction, under certain driving conditions. In the case of the limitedslip differential, the differential allows the deviation of the speedbetween shafts 144 coupled to the drive wheels 128 to be constrained.Consequently, traction under certain road conditions (e.g., low tractionconditions such as icy conditions, wet conditions, muddy conditions,etc.) may be increased due to the wheel speed deviation constraint.Additionally, in the torque vectoring dual clutch example, thedifferential may allow for torque delivered to the drive wheels to beindependently and more granularly adjusted to again increase tractionduring certain driving conditions. The torque vectoring dual clutch maytherefore provide greater wheel speed/torque control but may, in somecases, be more complex than the locking or limited slip differentials.

The vehicle 100 may also include a control system 150 with a controller152. The controller 152 includes a processor 154 and memory 156. Thememory 156 may hold instructions stored therein that when executed bythe processor cause the controller 152 to perform the various methods,control techniques, etc., described herein. The processor 154 mayinclude a microprocessor unit and/or other types of circuits. The memory156 may include known data storage mediums such as random access memory,read only memory, keep alive memory, combinations thereof, etc.Furthermore, it will also be understood that the memory 156 may includenon-transitory memory.

The controller 152 may receive various signals from sensors 158 coupledvarious locations in the vehicle 100 and the electric drive axle system102. The sensors may include a motor-generator speed sensor 160, anenergy storage device temperature sensor 162, an energy storage devicestate of charge sensor 164, wheel speed sensors 166, clutch positionsensors 168, etc. The controller 152 may also send control signals tovarious actuators 170 coupled at different locations in the vehicle 100and the electric drive axle system 102. For instance, the controller 152may send signals to the electric motor-generator 106 and the energystorage device 108 to adjust the rotational speed and/or direction(e.g., forward drive rotational direction and reverse drive rotationaldirection) of the motor-generator. The controller 152 may also sendsignals to the first clutch assembly 132 and the second clutch assembly134 to adjust the operational gear ratio in the gear train 104. Forinstance, the first clutch assembly 132 may be disengaged and the secondclutch assembly 134 may be engaged to place the second gear set 129 inan operational state (transferring rotational energy between theelectric motor-generator 106 and the output shaft 136). The othercontrollable components in the vehicle and gear system may function in asimilar manner with regard to command signals and actuator adjustment.For instance, the differential 110 may receive command signals from thecontroller 152.

The vehicle 100 may also include an input device 172 (e.g., a gearselector such as a gear stick, gear lever, etc., console instrumentpanel, touch interface, touch panel, keyboard, combinations thereof,etc.) The input device 172, responsive to driver input, may generate amode request indicating a desired operating mode for the gear train. Forinstance, in a use-case example, the driver may shift a gear selectorinto a gear mode (e.g., first gear mode or second gear mode) to generatea gear set modal transition request at the controller. In response, thecontroller commands gear train components (e.g., the first clutchassembly 132 and the second clutch assembly 134) to initiate atransition into a first gear mode, where the first gear set 127 isoperational, from a second gear mode, where the second gear set 129 isoperational, or vice versa. Other modality transitions have also beencontemplated such as a modal transition into a forward drive mode from areverse drive mode or vice versa responsive to driver input receivedfrom the input device 172. However, in other examples more automatedgear train mode transitions may be implemented. For instance, thecontroller may automatically place the gear train in the first gear modeor the second gear mode based on vehicle speed and/or load, for example.The controller 152 may also be configured to transition the electricdrive axle system 102 into a regenerative mode. In the regenerativemode, energy is extracted from the gear train using the electricmotor-generator 106 and transferred to the energy storage device 108.For instance, the electric motor-generator 106 may be placed in agenerator mode where at least a portion of the rotational energytransferred from the drive wheels to the generator by way of the geartrain is converted into electrical energy. A variety of different modalcontrol strategies have been contemplated. The power paths unfoldingduring the different system modes are discussed in greater detail hereinwith regard to FIGS. 18-20.

FIG. 2 shows an electric drive axle system 200. It will be appreciatedthat the electric drive axle system 200, shown in FIG. 2, serves as anexample of the electric drive axle system 102 shown in FIG. 1. As such,at least a portion of the functional and structural features of theelectric drive axle system 102 shown in FIG. 1 may be embodied in theelectric drive axle system 200 shown in FIG. 2 or vice versa, in certainembodiments.

The electric drive axle system 200 again includes an electricmotor-generator 202 and a gear train 204. The electric motor-generator202 has an electrical interface 206 which is illustrated as a bus bar inFIG. 2. However, other suitable electrical interfaces may be used, inother examples. The electric motor-generator 202 further includes ahousing 208. The gear train 204 may include an input shaft 210, anintermediate shaft 212, and an output shaft 214. The input shaft 210receives rotational input (forward or reverse drive rotation) from theelectric motor-generator 202, while the system is operating in forwardand reverse drive modes. Different gears in a gear train 204 are coupledto the different shafts, expanded upon in greater detail herein withregard to FIG. 3. Rotational axes 216, 218, and 220 of the input shaft210, the intermediate shaft 212, and the output shaft 214 are providedfor reference in FIG. 2 and FIGS. 3-21 when applicable. FIG. 2additionally shows a planetary gear assembly 222 rotationally coupled adifferential 224 in the gear train 204. The power paths through the geartrain 204 are discussed in greater detail herein. It will be appreciatedthat placing the planetary gear assembly 222 next to the differential224 allows less torque to be carried through the gear train 204,enabling the drive train to have fewer and/or smaller components, ifwanted.

The planetary gear assembly 222 can achieve a targeted gear ratio (e.g.,a relatively high gear ratio, such as a ratio greater than 20:1) in acompact arrangement relative to non-planetary gear arrangements. Thus,the planetary gear assembly can achieve a desired gear ratio with lesscomponents (e.g., gears and shafts) than non-planetary gear assemblies,if desired. Furthermore, in embodiments where the planetary gearassembly exhibits a relatively high torque output, the planetaryassembly can attain a more compact packaging due to the load sharingbetween the planet gears, if desired. Axis system 250 is illustrated inFIG. 2 as well as FIGS. 3-21, when appropriate, for reference. Thez-axis may be a vertical axis, the x-axis may be a lateral axis, and/orthe y-axis may be a longitudinal axis, in one example. However, the axesmay have other orientations, in other examples.

FIG. 3 shows the electric drive axle system 200 with the electricmotor-generator 202, input shaft 210, intermediate shaft 212, outputshaft 214, and gear train 204. The gear train 204 may include a firstgear 300 coupled to the input shaft 210. As described herein, thedescriptor “coupled to” may indicate one component is structurallycoupled to or formed with another component. For instance, the firstgear 300 may be machined from a flange on the input shaft 210, in oneexample, or separately manufactured and subsequently mechanicallyattached (e.g., welded, bolted, press-fit, etc.) to the input shaft 210.

A second gear 302 is coupled to the intermediate shaft 212. A third gear304 and a fourth gear 306 are also coupled to the intermediate shaft212. Additionally, a fifth gear 308 and a sixth gear 310 are coupled tothe output shaft 214. It will be understood, that during different modesof system operation different sets of gears may be operational. Toelaborate, the first gear 300, the second gear 302, the fourth gear 306,and the fifth gear 308 may be included in a first gear set 312. On theother hand, the first gear 300, the second gear 302, the third gear 304,and the sixth gear 310 may be included in a second gear set 314. A parkgear 311 may also be included in the gear train 204, in some examples.However, the gear sets may include different gear combinations, in otherexamples. It will be understood that the first and the second gear sets312 and 314 have different gear ratios. In this way, the gear train mayinclude multiple gear ratios to increase gear train adaptability.Additionally, the gear sets may share a few common gears (i.e., thefirst and second gears in the illustrated embodiment). Fixing the firstratio (i.e., the first and second gears) in the gear train can allow theaccuracy of the gears to be increased, if wanted, thereby reducingnoise, vibration, and harshness (NVH) in the axle system. However,embodiments where the gear sets do not include overlapping gears havebeen envisioned. Clutches, described in greater detail herein, areincluded in the gear train 204 to enable the first gear set 312 and thesecond gear set 314 to be coupled/decoupled to/from the output shaft214. In this way, the different gear sets may be operationally selectedto, for example, more aptly suite the driving environment and/orincrease electric motor efficiency. Thus, the first and second gear sets312 and 314 may be conceptually included in a selectable gear assembly316. A cutting plane A-A′ indicating the cross-sectional view of FIG. 8is provided in FIG. 3.

The planetary gear assembly 222 is shown in FIG. 3 rotationally coupledto the output shaft 214. FIG. 3 additionally illustrates thedifferential 224 in the gear train 204 rotationally coupled to theplanetary gear assembly 222. However, gear trains with gears positionedbetween the planetary assembly and the differential, etc. It will beappreciated that in some embodiments, the gear ratio corresponding tothe planetary gear assembly 222 may be greater than the gear ratiocorresponding to the first gear set 312 or the second gear set 314. Theplanetary gear assembly 222 allows a desired gear ratio to be realizedin a compact arrangement. For instance, the planetary gear assembly 222may achieve a relatively high gear ratio and space efficiency, ifdesired. However, non-planetary gear arrangements may be used, in otherexamples. Furthermore, the planetary gear assembly 222 and thedifferential 224 are shown positioned on a lateral side 322 of a housing208 the electric motor-generator 202. A lateral axis 324 of themotor-generator is provided for reference. Offsetting the output shaft214 and the intermediate shaft 212 from the input shaft 210 allows theplanetary gear assembly 222 to be positioned on the side 322 of themotor-generator. It will be appreciated that the planetary gear assemblymay be located adjacent to the motor's lateral side 322 due to theplanetary gear assembly's ability to be integrated into the gear trainwithout a mating gear parallel thereto, if wanted. In this way, theplanetary gear assembly may be placed in a spaced which has remainedunused in certain electrified gearboxes. Thus, positioning the planetarygear assembly on the side of the motor allows the compactness of theaxle system to be increased. As a result, the packaging constraintsarising during axle installation in the vehicle may pose less of anissue. However, in other examples, the planetary gear assembly 222 maybe positioned in other suitable locations. For instance, the planetarygear assembly may be coupled to a section of the output shaft extendingaway from the motor-generator.

FIG. 4 shows a side view of the electric drive axle system 200 with theinput shaft 210, intermediate shaft 212, and the output shaft 214. Acutting plane B-B′ indicating the cross-sectional view of FIG. 5, acutting plane C-C′ indicating the cross-sectional view of FIG. 6, and acutting plane D-D′ indicating the cross-sectional view of FIG. 7 areillustrated in FIG. 4.

FIG. 5 shows a cross-section view of the electric motor-generator 202and input shaft 210 in the electric drive axle system 200. The inputshaft 210 is shown transition fit with a rotor shaft 500. However, othersuitable coupling techniques have been contemplated, such as pressfitting, welding, splined engagement, etc. The rotor shaft 500 iscoupled to a rotor 501 designed to electromagnetically interact with astator 503 to generate forward drive rotational output, reverse driverotational output, and/or generate electrical energy during aregeneration mode.

A first bearing 502 and a second bearing 504 are shown coupled to theinput shaft 210 with the first gear 300 thereon. The bearings 502 and504 are positioned on opposing axial sides of the first gear 300, to forexample reduce shaft bending moments. However, other bearingarrangements have been envisioned such as a bearing arrangement with oneor two bearings on an outboard side of the first gear 300. As describedherein, a bearing is a component designed to enable rotation of thecomponent(s) to which it is attached and therefore may include rollingelements (balls, cylindrical rollers, tapered cylindrical rollers,etc.), races (e.g., inner and outer races), etc., to enable therotational functionality to be achieved. In one specific example, thefirst bearing 502 may be a floating bearing and/or may be coupled to theinput shaft 210 via a slip fit spline 506. In another specific example,the second bearing 504 may be a fixed bearing. However, other suitablebearing configurations may be used, in other examples, such as anarrangement where both of the bearings are fixed bearings, for instance.

Turning to FIG. 6, where the input shaft 210 and the first gear 300 areshown rotationally attached to the second gear 302 in the intermediateshaft 212 of the gear train 204 of the electric drive axle system 200.Therefore, during gear train operation, rotational motion is impartedbetween the first gear 300 and the second gear 302. The third gear 304and the fourth gear 306 attached to the intermediate shaft 212 are alsodepicted in FIG. 6. However, other gearings arrangements may be used, inother examples. Bearings 600 are shown positioned on opposing axialsides 602 of the intermediate shaft 212. The bearings 600 arespecifically illustrated as tapered roller bearings. However, othertypes of bearings and/or bearing arrangements may be used for theintermediate shaft, in other examples.

FIG. 7 shows a detailed cross-sectional view of the intermediate shaft212 and the output shaft 214 included in the electric drive axle system200. The sixth gear 310 is shown coupled to the output shaft 214. Thefifth gear 308 is arranged on a bearing 700 on the output shaft 214. Theplanetary gear assembly 222 and the differential 224 are also shown inFIG. 7. The differential 224 is depicted as a bevel gear differential,in FIG. 7, discussed in greater detail herein. However, planetary gear,spur, or helical gear differentials may be used, in other embodiments.

Referring to FIG. 8 showing a more detailed view of the output shaft 214and corresponding components in the gear train 204 of the electric driveaxle system 200. Specifically, the fifth gear 308, the sixth gear 310,the planetary gear assembly 222, and the differential 224 are againdepicted. The electric drive axle system 200 includes clutches allowingthe gear ratio in the gear train 204 delivered to the planetary gearassembly 222 to be adjusted, based on system operating conditions.Specifically, a first clutch assembly 800 is configured to rotationallycouple and decouple the fifth gear 308 to/from the output shaft 214 anda second clutch assembly 802 is configured to rotationally couple anddecouple the sixth gear 310 to/from the output shaft.

FIG. 9 shows a detailed view of the first clutch assembly 800 configuredto rotationally couple/decouple the fifth gear 308 to/from the outputshaft 214. To elaborate, the first clutch assembly 800 includes alocking clutch 900 and a one-way clutch 902, in the illustrated example.The one-way clutch 902 is designed to freely rotate about the outputshaft 214 when receiving rotational input in a first direction (reversedrive rotational direction) from the fifth gear 308 or when it isoverrun via the output shaft. The one-way clutch 902 is also configuredto transfer torque to the output shaft 214 when receiving rotationalinput in a second direction (e.g., front drive rotational direction)from the fifth gear 308. The one-way clutch 902 may be a sprag clutch,in one example. However, other suitable types of one-way clutches may beused in other examples, such as ratcheting clutches. Additionally, asection 903 of the output shaft 214 below the one-way clutch 902 may belocally thicker due to the contact stress and deflection of shaft alongthe one-way clutch, in one example. Further, in some examples, snaprings 905 may be used to axially retain the one-way clutch 902 and/orthe bearing 700.

An embodiment of a one-way clutch is shown in FIG. 21. The sprag clutch2100 includes a plurality of sprag mechanisms 2102 mounted on carrierrings 2104. The sprag mechanisms 2102 may be spring loaded and rotateabout axis 2106. The sprag mechanisms 2102 include curved surfaces 2108having asymmetric profiles. When the fifth gear (e.g., fifth gear 308,shown in FIG. 9) attached to the sprag clutch rotates in the forwarddrive direction, at a speed greater than the output shaft (e.g., outputshaft 214 shown in FIG. 9), the curved surfaces 2108 frictionally engagean outer surface of the output shaft and an inner surface of the fifthgear to allow the fifth gear and the output shaft to rotate in unison.Contrariwise, when the fifth gear is rotated in the reverse drivedirection or the output shaft speed exceeds the gear speed, the curvedsurfaces 2108 in the sprag mechanisms 2102 disengage and allow the fifthgear 308, shown in FIG. 9, to freewheel with regard to the output shaft214, referred to herein as a freewheel configuration. The sprag clutchallows for quick and robust engagement between the clutch and the shaftwhen transitioning from the freewheel configuration to the engagedconfiguration. The sprag clutch may also have less drag in the freewheelconfiguration when compared to other types of one-way clutches, such asone-way clutches including ratcheting mechanisms.

The locking clutch 900, illustrated in FIG. 9, is designed torotationally couple and decouple the fifth gear 308 from the outputshaft 214. To elaborate, the locking clutch 900 may be a dog clutch withteeth 904 on an axially adjustable shift collar 906 designed to matewith teeth 908 in the fifth gear 308 when engaged. Conversely, when thedog clutch is disengaged the teeth 904 on the shift collar 906 may bespaced away from the teeth 908 on the fifth gear 308. The bearing 700(e.g., needle roller bearing) coupled to the fifth gear 308 is alsoshown in FIG. 9. It will be appreciated that the bearing 700 may pilotthe one-way clutch 902. The shift collar 906 may be rotationallyattached to the output shaft 214 by way of an indexing shaft 910.Furthermore, the indexing shaft 910 may be attached to the output shaftvia press-fitting, a splined interface, combinations thereof, etc.However, the first clutch assembly 800 may take other forms, inalternate embodiments. For instance, the first clutch assembly may be afriction clutch, in an alternate example.

A thrust bearing 912 (e.g., needle roller thrust bearing) is also shownpositioned at an interface between the indexing shaft 910 and the fifthgear 308 to enable a desired spacing to be maintained between thecomponents while allowing rotation therebetween. Additionally, thethrust bearing 912 may be preloaded via a spring 914 (e.g., a wavespring, helical spring, elastomeric spring, etc.). However, othersuitable gear train arrangements may be used in other examples such asgear trains where the spring 914 and/or thrust bearing 912 are omitted.A bearing 916 (e.g., a fixed bearing) is also shown attached to anextension 918 (e.g., axial extension) of the fifth gear 308 interfacingwith the one-way clutch 902. However, in other examples the bearing 916may be omitted from the gear train. The bearing 916 is specificallydepicted as a ball bearing. The ball bearing may be used in the system,due to cost and packaging. However, the bearing 916 may be a sphericalroller bearing, a tapered roller bearing, four point contact bearing,etc., in other embodiments. In one example, the bearing 916 may be fixedon both sides to allow the spring 914 to apply a preload to the thrustbearing 912 and the sixth gear 310. The one-way clutch 902 is also shownpositioned between the extension 918 of the fifth gear 308 and an outersurface 919 of the output shaft 214. However, alternate locations of theone-way clutch have been contemplated.

The second clutch assembly 802 is depicted in FIG. 9 as a wet frictionclutch. Using a wet friction clutch enables load transfer in bothforward and reverse directions, allowing the drive train to forego alocking clutch in the second clutch assembly, in some instances.However, alternate types of clutches such as hydraulic clutches,electromagnetic clutches, and the like may be deployed, in otherarrangements. The wet friction clutch includes friction plates 920engaging one another when the clutch is activated to transfer rotationalenergy from the sixth gear 310 to the output shaft 214. Likewise, whenthe wet friction clutch is disengaged, the friction plates 920 arefrictionally decoupled and rotational energy transfer from the sixthgear 310 to the output shaft 214 is inhibited. To elaborate, a first setof friction plates 921 are coupled to the sixth gear 310 and a secondset of friction plates 923 are coupled to the output shaft 214 to enablecoupling/decoupling action in the clutch.

Various bearings may enable the wet friction clutch to be rotated aswell as provide axial and radial support to the clutch. The bearingcorresponding to the wet friction clutch may include for example, apilot bearing 922 (e.g., floating pilot bearing), a roller bearing 924(e.g., needle roller bearing, a thrust bearing 926 (e.g., needle rollerthrust bearing), and a roller bearing 928. However, other suitablebearing arrangements providing a desired amount of radial and axialsupport to the wet friction clutch and output shaft for the wet frictionclutch have been contemplated.

The wet second clutch assembly 802 (e.g., friction clutch) and thelocking clutch 900 may be adjusted via commands from a controller, suchas the controller 152 shown in FIG. 1, to induce engagement ordisengagement of each clutch. As such, the gear train's gear ratio maybe adjusted as desired based on vehicle operating conditions, driverinput, etc.

Referring again to FIG. 8, showing the planetary gear assembly 222rotationally coupled to the output shaft 214. FIG. 8 also illustratesthe planetary gear assembly 222 with a sun gear 810 rotationally coupledto output shaft 214. The sun gear 810 is rotationally coupled to planetgears 812 residing on planet pins 814 on a carrier 816. In turn, thecarrier 816 is shown coupled to the differential 224. However, planetaryarrangements with other components (e.g., carrier or annulus) coupled tothe output shaft 214 and other components (e.g., sun gear or annulus)coupled to the differential 224, have been envisioned. The planetarygear assembly 222 also includes an annulus 818 rotationally interactingwith the planet gears 812. Bearings 820 (e.g., needle roller bearings)arranged between the planet pins 814 and the planet gears 812 may allowthe planet gear to rotate. A thrust bearing 822 (e.g., needle rollerthrust bearing) may also be coupled to the sun gear 810 to enablerotation thereof and provide axial support thereto.

The annulus 818 may be held fixed to enable the planetary gear assembly222 to achieve a relatively high gear ratio. Thus, the annulus 818 mayinclude suitable features such as a spline 828 to enable the position ofthe annulus to be fixed. However, planetary gear arrangements wherealternate components are held fixed and alternate components are allowedto rotate may be utilized, in other examples. For instance, the annulusmay be allowed to freely rotate and the carrier may be held stationary,in one example, or the sun gear may be held stationary and the carrierand the annulus may be allowed to rotate, in other examples. In oneembodiment, the components in the planetary gear assembly that areallowed to rotate and held stationary may not be adjustable. Toelaborate, the components in the planetary gear assembly that areallowed to rotate and held substantially stationary may remain in thesame state (a substantially fixed state or a rotational state) duringgear train operation, in some embodiments. The planetary gear assemblycan therefore achieve even greater space efficiency, in such anembodiment. In other embodiments, planetary components whosefixed/rotational state can be adjusted during gear train operation havealso been contemplated. Thrust washers and/or bushings 830 may also bepositioned on opposing axial sides of the planet gears 812 to provideplanet gear spacing and support functionality.

A clutch assembly 832 configured to lock and unlock the differential 224may also be included in the gear train 204. The clutch assembly 832 may,in one example, include a dog clutch 834 configured to operate in alocked and unlocked configuration. In the locked configuration the dogclutch 834 causes the side gears 836 to rotate in unison. Conversely, inthe unlocked configuration, the dog clutch 834 allows the side gears 836to have rotational speed variance. One of the gears 836 may thereforeinclude teeth 837 mating/disengaging with/from teeth 839 in the dogclutch 834. The clutch assembly 832 may further include an electronicactuator 835 (e.g., solenoid) inducing engagement and disengagement ofthe clutch assembly 832. However, pneumatic or hydraulic clutchactuation may be utilized, in other embodiments.

FIG. 8 also shows the differential 224 rotationally coupled to an axle838. Specifically, the side gears 836 may be rotationally attached toaxle 838. The axle 838 is shown including a first shaft section 840which may be coupled to a first drive wheel and a second shaft section842 which may be coupled to a second drive wheel. However, in otherexamples, a continuous shaft may extend through the differential or theshaft may be partitioned into additional sections. The axle 838 may be abeam axle, enabling the load carrying capacity and the durability of theaxle to be increased, if wanted. However, non-rigid axle designs may beutilized, in other cases. Additionally, the axle 838 is positionedwithin an interior opening 841 of the output shaft 214 and is positionedco-axial therewith, to increase system compactness. However, off-axisaxle-output shaft layouts may be used, in some instances. A bearing 846is also shown coupled to a case 848 of the differential 224.Additionally, a bearing 849 is shown coupled to the planetary gearassembly 222 (e.g., the carrier 816). However, the bearing 849 may beomitted or placed in another suitable location, in other embodiments.

The case 848 is rotationally coupled to the carrier 816. In turn, thecase 848 is rotationally coupled to internal differential gearings. FIG.8 specifically shows the differential 224 embodied as a locking typedifferential (e.g., electronic locking differential). However, aspreviously discussed, alternate types of differentials have beencontemplated such limited slip differentials (e.g., electronic limitedslip differentials), differentials with a torque vectoring dual clutch,open differentials, etc. In the case of an open differential, thedifferential may share a common case with the planetary gear assemblyand the case may be sized and profiled to enable differential gearinstallation. Furthermore, the differential 224 depicted in FIG. 8includes bevel gears 860 attached via a bevel gear shaft 862.Additionally, in the illustrated embodiment, the bevel gears 860 arerotationally coupled to the side gears 836. However, planetary, spur,and helical gear type differentials may be used, in other examples.

FIG. 10 shows a detailed view of the second clutch assembly 802 (e.g.,wet friction clutch) in the gear train 204 and a lubrication system1000. The second clutch assembly 802 includes a friction clutch 1002, inthe embodiment illustrated in FIG. 10. However, as previously discussedalternate types of clutch assemblies have been contemplated.

The friction clutch 1002 includes a friction disk carrier 1004, theplurality of friction plates 920, a clutch drum 1006, the roller bearing928 (e.g., thrust roller bearing), and the pilot bearing 922 (e.g., ballbearing). A wave spring 1008 and a snap ring 1010 are also shown coupledto an axial side of the pilot bearing 922 to axially preload thebearing. However, other clutch arrangements have been contemplated, suchas clutch embodiments with a different quantity and/or types ofbearings, different mounting structures, different preload structures,etc. The friction disk carrier 1004 is fixedly coupled to the outputshaft 214. For instance, an inner surface 1012 of the friction diskcarrier 1004 may be press-fit onto an outer surface 1014 of the outputshaft 214.

The roller bearing 924 (e.g., needle roller bearing) is also shownpositioned between the clutch drum 1006 and the output shaft 214.Additionally, the thrust bearing 926 (e.g., needle roller thrustbearing) is shown coupled to the clutch drum 1006. The thrust bearing926 allows the clutch drum 1006 and the output shaft 214 toindependently rotate when the friction clutch 1002 is disengaged.However, as previously discussed, different bearing arrangementsproviding a desired degree of radial and/or axial support determinedbased on design parameters such as shaft and gearing sizing, shaft andgearing material construction, expected gear train operating speedrange, and the like, have been envisioned. The park gear 311 attached toindexing shaft 910 mounted on the output shaft 214 is also shown in FIG.10.

The sixth gear 310 is shown fixedly coupled to the clutch drum 1006. Toelaborate, the sixth gear 310 includes an inner surface 1016 coupled toan outer surface 1018 of the clutch drum 1006 radially outward from theplurality of friction plates 920.

The friction plates 920 include the first set of friction plates 921coupled to the clutch drum 1006. Conversely, the second set of frictionplates 923 are coupled to the friction disk carrier 1004. The differentsets of friction plates may frictionally engage and disengage to bringabout clutch engagement and disengagement. When the friction clutch 1002is engaged, the sixth gear 310 and the output shaft 214 co-rotate.However, when the friction clutch 1002 is disengaged the sixth gear 310and the output shaft 214 are allowed to independently rotate with regardto one another. The friction clutch 1002 may additionally include asupport plate 1020 which may be press-fit or otherwise coupled to theclutch drum 1006. A snap ring 1022 may also be provided to retain thesupport plate 1020 in a desired position. However, other clutcharrangements with differently profiled support plates, clutch drums,etc., may be used in other examples.

To induce clutch engagement/disengagement action, an actuator 1024(e.g., electromagnetic, hydraulic, or pneumatic actuator), schematicallyillustrated in FIG. 10, may be included in the friction clutch. Toelaborate, the actuator 1024 may be designed to axially extend andretract a piston 1026 through an opening 1027 (e.g., through holes) inthe clutch drum 1006. Although one piston and through hole are shown inFIG. 10, it will be appreciated that the actuator may include multiplepistons and through holes, a piston with multiple heads and throughholes, etc. Thus, the piston 1026 interacts with a pressure plate 1028to induced frictional engagement/disengagement of the friction plates920. Axial movement of the piston in direction 1030 thereforeprecipitates clutch engagement and axial movement of the piston indirection 1032 precipitates clutch disengagement. However, in otherembodiments, the piston and pressure plate may be positioned on theopposing side of the clutch.

The lubrication system 1000 is configured to supply a lubricant (e.g.,synthetic oil, non-synthetic oil, combinations thereof, etc.) to thefriction clutch 1002 and other gear train components, in some cases. Thelubrication system 1000 may include a reservoir 1034 and a pump 1036configured to generate lubricant flow in the system. Although the pump1036 and reservoir 1034 are schematically illustrated away spaced awayfrom each other, embodiments where the pump is integrated into thereservoir, have been contemplated. The pump 1036 may includeconventional components such as pistons, chambers, valves, seals,rotors, etc., to generate lubricant pressurization. It will also beunderstood, that the reservoir 1034 may be constructed as a sump toreceive lubricant from components in the gear train. The pump 1036 maybe controlled via a suitable controller, such as controller 152, shownin FIG. 1. The lubrication system 1000 may additionally include seals,valves (e.g., check valve, active valves, etc.), etc., in some cases.

The pump 1036 is in fluidic communication with a lubrication channel1038 positioned between an outer surface 1040 of first shaft section 840in the axle 838 and an inner surface 1042 of the output shaft 214. Thus,in one example, the lubrication channel 1038 may circumferentiallysurround the first shaft section 840. However, in other examples, thelubrication channel 1038 may be bounded in specific radial sectionsaround the first shaft section 840.

The lubrication channel 1038 include an outlet 1044 radially extendingthrough the output shaft 214. Although a single outlet is illustrated,it will be understood that in certain embodiments, the lubricationchannel may include a plurality of radial outlets opening into thefriction clutch. In such an embodiment, the outlets may be evenly spacedaround the output shaft, to avoid rotational imbalance, in someinstances.

The outlet 1044 is also shown radially extending through the frictiondisk carrier 1004. In this way, lubricant may be efficiently routed tothe friction plates 920. Specifically, the outlet 1044 is shown openinginto a section of the clutch below a portion of the friction platescoupled to the friction disk carrier 1004. Lubricant may flow radiallythrough the friction plates 920 once introduced into the frictionclutch. The sixth gear 310 is shown including a tapered section 1046,tapering in axial direction 1048, in the illustrated example. However,in other examples, the tapered section may be on the other axial side ofthe sixth gear 310. The clutch drum 1006 includes an opening 1050 (e.g.,radially aligned opening) positioned radially inward from the taperedsection 1046. In this way, outflow from the clutch's friction plates 920can be expelled from the friction clutch. Put another way, the sixthgear is back-drafted to enable lubricant outflow from the frictionclutch.

The clutch drum 1006 also includes the outer surface 1018 (e.g., pilotsurface) in face sharing contact with the inner surface 1016 of thesixth gear 310. Specifically, the sixth gear 310 may be press-fit andwelded to the outer surface 1018, in one example. However, in otherexamples, the sixth gear 310 may attached to the clutch drum via asplined interface, heavy pressed interface, welding, bolting, via a snapring, combinations thereof, etc.

Arrows 1052 indicate the general direction of lubricant flow through thelubrication system 1000. Thus, as illustrated, lubricant travels throughthe lubrication channel 1038 to the outlet 1044 extending through theoutput shaft 214 and the friction disk carrier 1004 into the frictionplates 920. From the friction plates 920, lubricant is directed throughthe opening 1050 in the clutch drum 1006 and through a channel below thetapered section 1046 of the sixth gear 310 and out of the frictionclutch. However, other suitable paths for lubricant routing have beenenvisioned, such as a path where lubricant is expelled on the otheraxial side of the clutch assembly.

FIG. 11 shows a detailed view of the output shaft 214 with openings 1100forming a portion of the outlet(s) 1038 of the lubrication channel 1038,shown in FIG. 10. As previously discussed, although one outlet 1044 isshown in FIG. 10, the lubrication system may include a plurality ofoutlets opening into the friction clutch. Continuing with FIG. 11,splines 1102 designed to mate with splines 1202 in the friction diskcarrier 1004, shown in FIG. 12, are also depicted in FIG. 11. However,in other examples, the friction disk carrier may be press-fit onto theoutput shaft. Additionally, splines 1104 designed to mate with splinesin the indexing shaft 910, shown in FIG. 10, are also depicted in FIG.11. However, the indexing shaft 910 may form an interference fit withthe output shaft, in other examples. Additionally, FIG. 11 illustratesthe surface 1106 on the output shaft 214 coupled to the pilot bearing922, depicted in FIG. 10.

FIG. 12 shows a detailed view of the friction disk carrier 1004. Thefriction disk carrier 1004 includes openings 1200 forming a portion ofthe outlets of the lubrication channel 1038, shown in FIG. 10. It willbe appreciated that when assembly, the openings 1200 in the frictiondisk carrier 1004 may be radially aligned with the openings 1100 in theoutput shaft 214, shown in FIG. 11. The friction disk carrier 1004 mayinclude interior splines 1202 configured to mate with the splines 1102in the output shaft 214, shown in FIG. 11 and exterior splines 1204configured to mate with splines in a portion of the friction plates 920,shown in FIG. 10.

FIG. 13 shows a detailed view of the clutch drum 1006. The clutch drum1006 includes openings 1300 radially extending therethrough and allowinglubricant outflow from the clutch. The clutch drum 1006 may also includesplines 1302 configured to mate with a portion of the friction plates920, shown in FIG. 10. An outer surface 1304 designed to attach (e.g.,press-fit, weld, etc.) to the sixth gear 310, shown in FIG. 10, isadditionally depicted in FIG. 13. The openings 1027 (e.g., throughholes) in the clutch drum 1006 is also shown in FIG. 13.

FIG. 14 shows a detailed view of the first clutch assembly 800. Theone-way clutch 902, locking clutch 900 with the shift collar 906,bearing 916, thrust bearing 912, park gear 311, indexing shaft 910,fifth gear 308, and bearing 700 are again illustrated. Another outlet1400 of the lubrication channel 1038 of the lubrication system 1000arranged between the output shaft 214 and the first axle shaft section840 is also depicted. Arrow 1402 indicates the general direction oflubricant flow through the outlet 1400. The outlet 1400 radially extendsthrough the output shaft 214 into a section of the first clutch assembly800 axially between the one-way clutch 902 and the bearing 700. In thisway, the lubrication system may provide lubricant to other components inthe drive axle. As a result, the lubrication system's capabilities areexpanded to reduce wear in other drive train components. However, inother examples, the outlet 1400 may be omitted from the lubricationsystem 1000.

FIGS. 15-16 depict different views of the fifth gear 308 including teeth1500, an inner surface 1502 that may be adjacent to sprags in theone-way clutch 902, shown in FIG. 14, and an axial extension 1504 thatmay be coupled to the bearing 916, shown in FIG. 14. The fifth gear 308is also shown with dog clutch teeth 904 designed to mate withcorresponding teeth 908 in the shift collar 906, shown in FIGS. 9 and14. The teeth 904 are shown in a “face” style arrangement designed foraxially engagement/disengagement. However, dog teeth having a “sleeve”type arrangement designed for radial engagement/disengagement, have beenenvisioned. As previously discussed, the shift collar is designed toaxially translate along the indexing shaft to induce clutchlocking/unlocking action. Thus, when the teeth are mated, the lockingclutch 900, shown in FIG. 14, is engaged, and when the teeth aredecoupled, the locking clutch is disengaged. The axial extension 1504and dog clutch teeth 904 are positioned on opposing axial sides of thefifth gear 308, in the illustrated embodiment. However, in otherexamples, the axial extension and the teeth may be positioned on thesame axial side of the fifth gear.

FIG. 17 shows a method for operation of a lubrication system in anelectric drive axle. The method 1700 may be implemented via one or moreof the lubrication systems and electric drive axles described above withregard to FIGS. 1-16, in one embodiment, or may be implemented byanother suitable lubrication system and electric drive axle, in otherembodiments. Furthermore, the method 1700 may be implemented viainstructions stored in memory (e.g., non-transitory memory) executableby a processor.

At 1702, the method includes flowing lubricant through a lubricationchannel between an outer surface of an axle shaft and an inner surfaceof an output shaft. Next at 1704, the method includes flowing lubricantfrom the lubrication channel to an interior of a first clutch (e.g.,friction clutch) and at 1706, the method includes flowing lubricant outof the first clutch through a gear coupled to the first clutch. In thisway, the first clutch's lubrication needs may be met, thereby increasingclutch longevity. It will also be appreciated that in some example, thefriction clutch may be actuated while it is being lubricated. Thus, themethod may include in one example, actuating a piston extending througha radially aligned hole in a clutch drum to engage or disengage aplurality of friction plates in the first clutch.

Next at 1708 the method may include flowing the lubricant from thelubrication channel to a second clutch (e.g., one-way clutch), allowingadditional components in the drive axle to be lubricated via a commonlubrication channel located between the axle shaft and the output shaft.Method 1700 enables lubricant to be efficiently routed to differentdrive axle clutches to achieve a targeted amount of componentlubrication in the drive axle.

FIGS. 18-20 show the gear train 204 operating in different modes. Assuch, the gear train 204 may be placed in different operational modesvia a controller, such as the controller 152, shown in FIG. 1. The modesmay include a first gear mode where the first gear set 312, shown inFIG. 3, transfers rotational energy between the electric motor-generator202 and the planetary gear assembly 222. The modes may also include asecond gear mode where the second gear set 314, shown in FIG. 3,transfers rotational energy between the electric motor-generator 202 tothe planetary gear assembly 222. The modalities may also be partitionedbased on reverse and forward drive motor arrangement. To elaborate, theelectric motor-generator 202 may produce rotational output in a firstdirection corresponding to forward drive and may produce rotationaloutput in a second direction opposing the first corresponding to reversedrive. As such, the gear train modalities may include a forward drivefirst gear mode, a reverse drive first gear mode, a forward drive secondgear mode, and/or a reverse drive second gear mode. It will also beunderstood that the gear train may be operated in a regenerative modewhere torque input from the drive wheels, such as the drive wheels 128shown in FIG. 1, is transferred to the electric motor-generator and theelectric motor-generator converts at least a portion of the drivetrain's rotational energy into electrical energy. In turn, in theregenerative mode the electric energy may be transferred from themotor-generator to an energy storage device, such as the energy storagedevice 108 shown in FIG. 1.

Turning to FIG. 18, illustrating the gear train 204 of the electricdrive axle system 200 arranged in the forward drive first gear modewhere the electric motor-generator 202 produces forward drive rotationaloutput, the second clutch assembly 802 is disengaged, and the firstclutch assembly 800 is engaged (e.g., configured to transfer energy fromthe fifth gear 308 to the output shaft 214 via the one-way clutch 902).The power path in the forward drive first gear mode of the gear train204 is indicate via arrows 1800. Thus, in the forward drive first gearmode, rotational energy is transferred from the electric motor-generator202 to the first gear 300, from the first gear to the second gear 302,from the fourth gear 306 to the fifth gear 308, from the fifth gearthrough the first clutch assembly 800 (e.g., through the one-way clutch902) to the output shaft 214, from the output shaft to the planetarygear assembly 222, from the planetary gear assembly to the differential224, and from the differential to the axle 838.

FIG. 19 shows the gear train 204 of the electric drive axle system 200arranged in the forward drive second gear mode where the electricmotor-generator 202 produces forward drive rotational output, the secondclutch assembly 802 is engaged, and the first clutch assembly 800 isdisengaged (e.g., the locking clutch 900 is disengaged and the one-wayclutch 902 is overrun). It will be understood, that the one-way clutch902 is overrun due to the ratio of the mesh between the third gear 304and sixth gear 310 being lower than the ratio of the mesh between thefourth gear 306 and the fifth gear 308, resulting in no load beingtransferred between the fourth and fifth gear. The power path in theforward drive second gear mode of the gear train 204 is indicate viaarrows 1900. Thus, in the forward drive second gear mode, rotationalenergy is transferred from the electric motor-generator 202 to the firstgear 300, from the first gear to the second gear 302, from the thirdgear 304 to the sixth gear 310, from the sixth gear through the secondclutch assembly 802 to the output shaft 214, from the output shaft tothe planetary gear assembly 222, from the planetary gear assembly to thedifferential 224, and from the differential to the axle 838.

FIG. 20 shows the gear train 204 of the electric drive axle system 200arranged in the regenerative first gear mode where the electricmotor-generator 202 generates electrical energy from drive wheel torquetransferred to the motor-generator through the gear train 204.Additionally, in the regenerative first gear mode the second clutchassembly 802 is disengaged, and the first clutch assembly 800 is engaged(e.g., configured to transfer energy from the fifth gear 308 to theoutput shaft 214 via the locking clutch 900). The power path in theregenerative first gear mode of the gear train 204 is indicate viaarrows 2000. As such, in the regenerative first gear mode, rotationalenergy is transferred from the differential 224 to the planetary gearassembly 222, from the planetary gear assembly to the output shaft 214,from the output shaft to the fifth gear 308 through the first clutchassembly 800 (e.g., through the locking clutch 900 bypassing the one-wayclutch 902), from the fifth gear to the fourth gear 306, from the secondgear 302 to the first gear 300 and then to the electric motor-generator202.

It will be appreciated that during a reverse first gear mode, the powerpath through the gear train 204 may be similar to the power path shownin FIG. 20. For instance, the power path in the reverse first gear modemay travel through the similar components to the power path denoted viaarrows 2000. However, in the reverse power path the arrows are reversed.Therefore, in the reverse first gear mode the second clutch assembly 802may be disengaged, and the first clutch assembly 800 may be engaged(e.g., configured to transfer energy from the fifth gear 308 to theoutput shaft 214 via the locking clutch 900).

The electric drive axles and lubrication systems described herein havethe technical effect of providing a lubrication system that spaceefficiently routes lubricant to desired component to reduce friction inthe component while maintaining a desired amount of drive axlecompactness, in some cases.

FIGS. 1-21 show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Additionally, elements co-axial withone another may be referred to as such, in one example. Further,elements shown intersecting one another may be referred to asintersecting elements or intersecting one another, in at least oneexample. Further still, an element shown within another element or shownoutside of another element may be referred as such, in one example. Inother examples, elements offset from one another may be referred to assuch.

The invention will be further described in the following paragraphs. Inone aspect, an electric drive axle system is provided that comprises agear train configured to rotationally attach to an electricmotor-generator, the gear train comprising: an output shaft having afirst clutch arranged thereon and configured to selectively rotationallycouple a first gear to the output shaft; where the first gear isconfigured to receive torque from the electric motor-generator; andwhere the output shaft is rotationally coupled to a gear assembly, thegear assembly is rotationally coupled to a differential, and thedifferential is rotationally coupled to an axle shaft arranged co-axialwith the output shaft; and a lubrication channel extending between theoutput shaft and the axle shaft and including a first outlet extendingthrough the output shaft and opening into the first clutch.

In another aspect, a method for operating a lubrication system in anelectric drive axle is provided that comprises flowing a lubricantthrough a lubrication channel between an outer surface of an axle shaftand an inner surface of an output shaft; flowing the lubricant from thelubrication channel to an interior of a first clutch; and flowing thelubricant out of the first clutch through a gear coupled to the firstclutch; where the output shaft is rotationally coupled to a planetarygear assembly; and where the planetary gear assembly is directly coupledto a differential.

In yet another aspect, an electric drive axle system is provided thatcomprises a gear train configured to rotationally attach to an electricmotor-generator, the gear train comprising: an output shaft having a wetfriction clutch arranged thereon and configured to selectivelyrotationally couple a gear to the output shaft; where the gear isconfigured to receive torque from the electric motor-generator; wherethe output shaft is rotationally coupled to a planetary gear assembly,the planetary gear assembly is directly rotationally coupled to adifferential and the differential is coupled to a beam axle arrangedco-axial with the output shaft; and a lubrication conduit extendingbetween the output shaft and the axle and including a first outletopening into a plurality friction plates in the wet friction clutch.

In any of the aspects or combinations of the aspects, where thelubrication channel may circumferentially surround an outer surface ofthe axle.

In any of the aspects or combinations of the aspects, the first gear mayinclude a tapered inner surface configured to outflow the lubricant fromthe first clutch.

In any of the aspects or combinations of the aspects, the first gear maybe coupled to a section of a clutch drum radially outward from aplurality of friction plates.

In any of the aspects or combinations of the aspects, the first outletof the lubrication channel may extend radially through a friction diskcarrier positioned radially inward from a plurality of friction platesin the first clutch.

In any of the aspects or combinations of the aspects, the lubricationchannel may include a second outlet extending through the output shaftadjacent to a second clutch.

In any of the aspects or combinations of the aspects, the second clutchmay be a one-way clutch.

In any of the aspects or combinations of the aspects, the second outletextending through the output shaft adjacent to the second clutch may beadjacent to a roller bearing coupled to a second gear on the outputshaft.

In any of the aspects or combinations of the aspects, the axle may be abeam axle and where the gear assembly is a planetary gear assembly.

In any of the aspects or combinations of the aspects, the planetary gearassembly may be directly coupled to the differential without anyintervening components positioned therebetween.

In any of the aspects or combinations of the aspects, the first clutchmay be a friction clutch, the gear may include a tapered inner surface,and the lubricant may outflow through a conduit formed between thetapered inner surface and a section of a clutch drum positioned radiallyoutward from the plurality of friction plates in the friction clutch.

In any of the aspects or combinations of the aspects, the method mayfurther comprise actuating a piston extending through a radially alignedhole in a clutch drum to engage or disengage the plurality of frictionplates in the first clutch.

In any of the aspects or combinations of the aspects, the method mayfurther comprise flowing the lubricant from the lubrication channel to asecond clutch.

In any of the aspects or combinations of the aspects, the gear may becoupled to a section of a clutch drum radially outward from a pluralityof friction plates and where the gear may include a tapered innersurface configured to outflow the lubricant from the wet frictionclutch.

In any of the aspects or combinations of the aspects, the first outletof the lubrication channel may extend radially through a friction diskcarrier positioned radially inward from a plurality of friction platesin the wet friction clutch.

In any of the aspects or combinations of the aspects, the lubricationchannel may include a second outlet extending through the output shaftadjacent to a one-way clutch.

In any of the aspects or combinations of the aspects, the axle may be abeam axle, the gear assembly may be a planetary gear assembly, and theplanetary gear assembly may be directly coupled to the differentialwithout any intervening components positioned therebetween.

In any of the aspects or combinations of the aspects, the differentialmay be a locking differential configured to rotationally lock and unlockaxle shaft sections.

In another representation, a lubrication system is provided for anelectric drive axle that comprises a circumferential lubricant conduitbounded between an axle shaft and an output shaft of a gearbox with aplanetary gear assembly directly coupled to a differential coupled to abeam axle, the lubrication system further including a radial lubricationconduit extending from the circumferential lubrication conduit into aregion radially inward from a plurality of friction disks a wet frictionclutch.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevant artsthat the disclosed subject matter may be embodied in other specificforms without departing from the spirit of the subject matter. Theembodiments described above are therefore to be considered in allrespects as illustrative, not restrictive.

Note that the example control and estimation routines included hereincan be used with various powertrain and/or vehicle systemconfigurations. The control methods and routines disclosed herein may bestored as executable instructions in non-transitory memory and may becarried out by the control system including the controller incombination with the various sensors, actuators, and other vehiclehardware. Further, portions of the methods may be physical actions takenin the real world to change a state of a device. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example examples described herein, but is provided forease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the vehicle control system, where the describedactions are carried out by executing the instructions in a systemincluding the various vehicle hardware components in combination withthe electronic controller. One or more of the method steps describedherein may be omitted if desired.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific examples are notto be considered in a limiting sense, because numerous variations arepossible. For example, the above technology can be applied topowertrains that include different types of propulsion sources includingdifferent types of electric machines and transmissions. The subjectmatter of the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

As used herein, the terms “approximately” and “substantially” areconstrued to mean plus or minus five percent of the range unlessotherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. An electric drive axle system, comprising: a gear train configured torotationally attach to an electric motor-generator, the gear traincomprising: an output shaft having a first clutch arranged thereon andconfigured to selectively rotationally couple a first gear to the outputshaft; where the first gear is configured to receive torque from theelectric motor-generator; and where the output shaft is rotationallycoupled to a gear assembly, the gear assembly is rotationally coupled toa differential, and the differential is rotationally coupled to an axleshaft arranged co-axial with the output shaft; and a lubrication channelextending between the output shaft and the axle shaft and including afirst outlet extending through the output shaft and opening into thefirst clutch.
 2. The electric drive axle system of claim 1, where thelubrication channel circumferentially surrounds an outer surface of theaxle.
 3. The electric drive axle of claim 1, where the first gearincludes a tapered inner surface configured to outflow the lubricantfrom the first clutch.
 4. The electric drive axle of claim 3, where thefirst gear is coupled to a section of a clutch drum radially outwardfrom a plurality of friction plates.
 5. The electric drive axle systemof claim 1, where the first outlet of the lubrication channel extendsradially through a friction disk carrier positioned radially inward froma plurality of friction plates in the first clutch.
 6. The electricdrive axle system of claim 1, where the lubrication channel includes asecond outlet extending through the output shaft adjacent to a secondclutch.
 7. The electric drive axle system of claim 6, where the secondclutch is a one-way clutch.
 8. The electric drive axle system of claim7, where the second outlet extending through the output shaft adjacentto the second clutch is adjacent to a roller bearing coupled to a secondgear on the output shaft.
 9. The electric drive axle system of claim 1,where the axle is a beam axle and where the gear assembly is a planetarygear assembly.
 10. The electric drive axle system of claim 9, where theplanetary gear assembly is directly coupled to the differential withoutany intervening components positioned therebetween.
 11. A method foroperating a lubrication system in an electric drive axle, comprising:flowing a lubricant through a lubrication channel between an outersurface of an axle shaft and an inner surface of an output shaft;flowing the lubricant from the lubrication channel to an interior of afirst clutch; and flowing the lubricant out of the first clutch througha gear coupled to the first clutch; where the output shaft isrotationally coupled to a planetary gear assembly; and where theplanetary gear assembly is directly coupled to a differential.
 12. Themethod of claim 11, where the first clutch is a friction clutch, thegear includes a tapered inner surface, and the lubricant outflowsthrough a conduit formed between the tapered inner surface and a sectionof a clutch drum positioned radially outward from a plurality offriction plates in the friction clutch.
 13. The method of claim 11,further comprising actuating a piston extending through a radiallyaligned hole in a clutch drum to engage or disengage a plurality offriction plates in the first clutch.
 14. The method of claim 11, furthercomprising flowing the lubricant from the lubrication channel to asecond clutch.
 15. An electric drive axle system, comprising: a geartrain configured to rotationally attach to an electric motor-generator,the gear train comprising: an output shaft having a wet friction clutcharranged thereon and configured to selectively rotationally couple agear to the output shaft; where the gear is configured to receive torquefrom the electric motor-generator; where the output shaft isrotationally coupled to a planetary gear assembly, the planetary gearassembly is directly rotationally coupled to a differential, and thedifferential is coupled to a beam axle arranged co-axial with the outputshaft; and a lubrication conduit extending between the output shaft andthe axle and including a first outlet opening into a plurality offriction plates in the wet friction clutch.
 16. The electric drive axlesystem of claim 15, where the gear is coupled to a section of a clutchdrum radially outward from the plurality of friction plates and wherethe gear includes a tapered inner surface configured to outflow thelubricant from the wet friction clutch.
 17. The electric drive axlesystem of claim 15, where the first outlet of the lubrication channelextends radially through a friction disk carrier positioned radiallyinward from the plurality of friction plates in the wet friction clutch.18. The electric drive axle system of claim 15, where the lubricationchannel includes a second outlet extending through the output shaftadjacent to a one-way clutch.
 19. The electric drive axle system ofclaim 15, where the planetary gear assembly is directly coupled to thedifferential without any intervening components positioned therebetween.20. The electric drive axle system of claim 19, where the differentialis a locking differential configured to rotationally lock and unlockaxle shaft sections.